Energy based pulse position detector for telephone wire networks

ABSTRACT

A system for detecting a pulse position is provided in a telephone wire network. An absolute value detector determines the absolute value of a received pulse signal supplied from a telephone wire, and produces a waveform envelope. A low-pass filter filters out high frequency components of the envelope. An integrator performs the time integration of the filtered envelope to produce an integrated waveform representing the energy of the received pulse signal. A slicing circuit determines when the integrated waveform crosses threshold level to detect the time position corresponding to the arrival time of the received pulse signal. The arrival time position is translated into a digital value representing data received form the telephone wire.

FIELD OF THE INVENTION

This application relates to data communications, and more specifically,to pulse position detectors for telephone wire networks.

BACKGROUND ART

In recent years there has been a huge increase in the demand forcost-effective communications networks. One of such networks is atelephone wire network that uses telephone line wiring existing in abuilding, such as Plain Old Telephone Service (POTS) line wiring, as amedium for the data transmission between computers.

In telephone wire networks, the arrival position in time of a receivedband limited pulse may be used to convey digital information. Thewaveform of a received band limited pulse is illustrated in FIG. 1.Conventionally, the arrival position of a received pulse is detectedusing a waveform envelope representing the absolute value of thereceived signal (FIG. 2). The envelope is supplied to a slicing circuithaving a threshold level selected to identify the arrival position ofthe received pulse. When the envelope crosses the threshold level, theslicing circuit detects the arrival position of the pulse.

However, in telephone wire networks, a received envelope waveformdepends largely on the wiring topology. As the wiring topology may causemultiple signal reflections, the shape of a received pulse may be sodistorted that the envelope will have multiple localized maximum points.In addition, the wiring topology varies from place to place. Therefore,the distortion of the received pulse is unpredictable.

FIG. 3 illustrates the waveform of a received pulse signal havingmultiple localized maximum points due to wiring topology. FIG. 4illustrates the waveform envelope of such a pulse signal. In response tothe waveform envelope having multiple maximum points, a slicing circuitmay identify multiple pulse positions, at which the envelope crosses athreshold level. As a result, a unique time value for the arrivalposition of a received pulse cannot be detected. This can cause datarecovery errors.

Thus, it would be desirable to provide a pulse position detector capableof identifying a unique pulse arrival position even if the receivedpulse is highly distorted.

DISCLOSURE OF THE INVENTION

Accordingly, the advantage of the present invention is in providing apulse position detector capable of identifying a unique arrival positionof a receive pulse, even if the pulse is highly distorted.

This and other advantages of the present invention are achieved at leastin part by providing a pulse position detector that comprises an inputcircuit for receiving an incoming pulse signal. For example, theincoming pulse signal may be supplied from Plain Old Telephone Serviceline wiring in a building. An integrator performs the integration overtime of a receive signal supplied from the input circuit to produce anintegrated signal representing energy of the incoming pulse signal. Aslicing circuit provides pulse position indication when the integratedsignal reaches a threshold level.

In accordance with a preferred embodiment of the invention, the inputcircuit may comprise an absolute value detector for producing anenvelope representing the absolute value of received pulse signalamplitude. A filter may be provided for filtering out high frequencycomponents of the envelope. The integrator performs integration of thefiltered envelope supplied from the filter. The slicing circuit maycomprise a comparator for producing a pulse position indication signalwhen the integrated signal reaches the threshold level.

A control circuit may determine levels of receive signals supplied fromthe input circuit to establish the threshold level in the slicingcircuit. The control circuit may reset the integrator when theintegrated signal reaches the threshold level.

Further, the control circuit may be coupled to the input circuit todetermine a noise level in the absence of an information signal. A noiselevel signal representing the noise level may be supplied to theintegrator to prevent it from performing the integration of the receivesignal until the receive signal exceeds the noise level.

When the integrated signal reaches the threshold level, the controlcircuit may be supplied with the pulse position indication signal fromthe slicing circuit to produce a bit pattern identifying the position intime of the incoming pulse signal. This bit pattern corresponding todata represented by the incoming pulse signal may be transferred to adata network.

In accordance with another aspect of the invention, a telephone wirenetwork for providing data communications over telephone line wiring ina building may comprise a pulse position detector that detects theposition in time of a pulse supplied from the telephone line wiring. Amedia access controller transfers a digital value representing the timeposition to a data network that delivers incoming data to an addressee.The pulse position detector in the telephone wire network may include

an input circuit coupled to the telephone line wiring, an integrator forperforming integration in time of a receive signal supplied from theinput circuit to produce an integrated signal representing energy of theincoming pulse, a slicing circuit for producing a time indication signalwhen the integrated signal reaches a preset threshold level, and anoutput circuit responsive to the time indication signal for producingthe digital value transferred to the media access controller.

In accordance with a method of the present invention the following stepsare carried out for detecting position in time of an incoming pulsesupplied from telephone line wiring:

producing an envelope representing the absolute value of incoming pulseamplitude,

integrating the envelope over time to produce an integrated signalproportional to energy of the incoming pulse, and

detecting a moment when the integrated signal reaches a preset thresholdlevel to indicate a position in time corresponding to arrival of theincoming pulse.

Still other objects and advantages of the present invention will becomereadily apparent to those skilled in this art from the followingdetailed description, wherein only the preferred embodiment of theinvention is shown and described, simply by way of illustration of thebest mode contemplated of carrying out the invention. As will berealized, the invention is capable of other and different embodiments,and its several details are capable of modifications in various obviousrespects, all without departing from the invention. Accordingly, thedrawings and description are to be regarded as illustrative in nature,and not as restrictive.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a waveform illustrated a band limited pulse the arrival timeposition of which may be used to convey digital information.

FIG. 2 is a waveform of an envelope representing the absolute value ofthe received pulse.

FIG. 3 illustrates a waveform of a received pulse signal in a telephonewire network.

FIG. 4 illustrates a waveform of the pulse signal envelope.

FIG. 5 illustrates a telephone wire network having a pulse positiondetector of the present invention.

FIG. 6 is a block diagram of the pulse position detector of the presentinvention.

FIG. 7 illustrates waveforms of receive signal envelope and integratedsignal supplied to a slicer.

BEST MODE FOR CARRYING-OUT THE INVENTION

Although the invention has general applicability in the field of dataprocessing, the best mode for practicing the invention is based in parton the realization of a pulse position detector in a telephone wirenetwork that uses telephone wiring, such as Plain Old Telephone Service(POTS) line wiring existing in a building, as a medium for the datatransmission between computers.

As illustrated in FIG. 5, a pulse position detector 2 may be arranged atreceiving end of a telephone wire network that transmits data overtelephone line wiring that connects multiple telephone terminals such astelephone sets in a building. A transmitting station converts transmitdata into pulse signals propagating over telephone line wiring in abuilding. The pulse position detector 2 detects the position in time ofpulses received from a telephone line wire to recover the transmit data.For example, the pulse position detector 2 may identify the arrivalposition in time of received pulses. The arrival time position istranslated into the unique bit pattern representing the transmit data.For example, the pulse position detector 2 may store a translation tablehaving a unique bit pattern for each time slot in which a pulse mayarrive. The bit pattern corresponding to the time slot, in which thereceived pulse has arrived, represents recovered digital data.

The bit pattern produced by the pulse position detector is supplied to amedia access controller (MAC) 4, such as AM79C940 Media AccessController for Ethernet (MACE) manufactured by Advanced Micro Devices,Inc. The MAC 4 transfers the recovered digital data to a datacommunications network 6, such as an Ethernet (ANSI/IEEE 802.3) network,for delivering to the addressee.

Referring to FIG. 6, the pulse position detector 2 coupled to thetelephone wire via a telephone coupler 20 comprises an amplifier 22 thatamplifies a pulse signal received from the telephone wire to anamplitude sufficient for further processing. An absolute value envelopedetector 24 coupled to the output of the amplifier 22 determines theabsolute value of the received signal and produces the waveform enveloperepresenting the absolute value of the received signal. Timing diagramsshown in FIG. 7 illustrate the receive waveform envelope produced by thedetector 24. A low-pass filter 26 is coupled to the envelope detector 24for filtering out high-frequency components of the receive waveformenvelope.

The filter 26 supplies the filtered waveform envelope to an integrator28 which performs the mathematical process of integration over time toproduce an integrated signal proportional to the energy of the receivedpulse signal. FIG. 7 illustrates the waveform of the integrated signalat the output of the integrator 28. The integrator 28 may be implementeddigitally or with an analog integrating circuit.

A slicer 30 is coupled to the output of the integrator 28 to detect whenthe integrated waveform crosses a preset threshold level. For example,the slicer may be implemented with an analog comparator. Alternatively,the slicer may be a digital device for detecting the moment when theintegrated waveform value reaches a preset threshold value.

A control logic 32 coupled to the slicer 30 provides a slice thresholdsignal that defines a threshold level for slicing the integratedwaveform. For example, the control logic 32 may measure levels ofpreviously received signals to determine an optimum threshold level fora currently received pulse. The control logic 32 sets the thresholdlevel higher than a noise level but lower than the maximum level of thewaveform envelope. For example, the control logic 32 may use waveformenvelops supplied from the output of the filter 26 to establish athreshold level.

When the slicer 30 detects that the integrated signal reaches thethreshold level, the slicer 30 produces a slice time indication signalsupplied to the control logic 32. The slice time indication signalcorresponds to the arrival position in time of the received pulsesignal.

In response to the slice time indication signal, the control logic 32produces a clear signal supplied to the integrator 28 to reset it. Asshown in FIG. 7, when the integrated signal reaches the threshold, thereset of the integrator 28 causes the integrated value to fall topractically zero level. As a result the integrator 28 is ready toperform the integration of the next receive waveform envelope.

In addition, the control logic 32 may produce a noise level signalsupplied to the integrator 28 to set a noise level defining a minimumoperating level of the integrator 28. The control logic 32 establishesthe noise level based on noise detected at the output of the filter 26in the absence of an information signal. The noise level signal preventsthe integrator 28 from performing the integration until the receivewaveform envelope exceeds the noise level. As a result, the accuracy ofthe integration is improved.

Based on the slice time indication signal produced by the slicer 30, thecontrol logic 32 determines a digital value corresponding to datareceived from the telephone wire. The control logic 32 may be aprogrammable gate array device having registers and memory areas forhandling signal and noise levels detected at the output of the filter28, and processing the slice time indication signals produced by theslicer 30.

The slice time indication signal represents the arrival position in timeof a received pulse. The control logic 30 compares the time position ofthe currently received pulse with time positions of previously receivedpulses, and determines the time slot, in which the current pulse hasarrived. The control logic 30 may comprise a translation table thatcontains a unique bit pattern for each time slot. Based on thedetermined time slot, the control logic 30 finds a bit patterncorresponding to the arrival time of the received pulse. This bitpattern represents data received from the telephone wire. The determinedbit pattern may be transferred to the MAC 4 that provides interface tothe data network 6.

Thus, the system of the present invention produces an integratedwaveform representing the energy of a pulse received from a telephonewire to detect the time position of the received pulse. As theintegrated waveform always has a positive slope on the leading edge, athreshold in a slicing circuit will always correspond to a uniquearrival time position, even if the received pulse is highly distorteddue to multiple reflections in a telephone wire network.

There accordingly has been described a system for detecting a pulseposition in a telephone wire network. A receive pulse signal is suppliedfrom the telephone wiring to an absolute value detector that determinesthe absolute value by pulse signal amplitude, and produces a waveformenvelope. A low-pass filter filters out high frequency components of theenvelope. An integrator performs the time integration of the filteredenvelope to produce an integrated waveform representing the energy ofthe received pulse signal. A slicing circuit determines when theintegrated waveform crosses a threshold level to detect the timeposition corresponding to the arrival time of the received pulse signal.The arrival time position is translated into a digital valuerepresenting data received from the telephone wire.

In this disclosure, there are shown and described only the preferredembodiments of the invention, but it is to be understood that theinvention is capable of changes and modifications within the scope ofthe inventive concept as expressed herein.

What is claimed is:
 1. A pulse position detector in a telephone wirenetwork, comprising:an input circuit for receiving an incoming pulsesignal, an integrator for integrating over time a receive signalsupplied from said input circuit to produce an integrated signalrepresenting energy of the incoming pulse signal, and a slicing circuitfor producing a pulse position signal representing a position in time ofthe incoming pulse signal when the integrated signal reaches a thresholdlevel.
 2. The pulse position detector of claim 1, wherein said inputcircuit comprises an absolute value detector for producing an enveloperepresenting the absolute value of received pulse signal amplitude. 3.The pulse position detector of claim 2, wherein said input circuitfurther comprises a filter for filtering out high frequency componentsof said envelope.
 4. The pulse position detector of claim 3, whereinsaid integrator performs integration of said filtered envelope suppliedfrom said filter.
 5. The pulse position detector of claim 4, whereinsaid slicing circuit comprises a comparator for producing a slice timeindication signal when said integrated signal reaches the thresholdlevel.
 6. The pulse position detector of claim 1, further comprising acontrol circuit responsive to receive signals supplied from the inputcircuit for establishing the threshold level in said slicing circuit. 7.The pulse position detector of claim 6, wherein said control circuit isadapted to reset said integrator when said integrated signal reaches thethreshold level.
 8. The pulse position detector of claim 6, wherein saidcontrol circuit is coupled to said input circuit to determine a noiselevel.
 9. The pulse position detector of claim 8, wherein said controlcircuit is adapted to supply said integrator with a noise level signalrepresenting said noise level.
 10. The pulse position detector of claim9, wherein said integrator is prevented from performing integration ofsaid receive signal until said receive signal exceeds said noise level.11. The pulse position detector of claim 6, wherein said control circuitis responsive to said pulse position signal for producing a bit patternidentifying the position in time of said incoming pulse signal.
 12. Thepulse position detector of claim 11, wherein said bit pattern istransferred to a data network as data represented by said incoming pulsesignal.
 13. The pulse position indicator of claim 12, wherein saidincoming pulse signal is supplied from Plain Old Telephone Service linewiring in a building.
 14. A telephone wire network for providing datacommunications over telephone line wiring in a building, comprising:apulse position detector responsive to an incoming pulse supplied fromthe telephone line wiring for detecting position in time of said pulseand producing a digital value representing said position in time, and amedia access controller responsive to said digital value for providingan addressee with incoming data, said pulse position detector including:an input circuit coupled to the telephone line wiring, an integrator forperforming integration in time of a receive signal supplied from saidinput circuit to produce an integrated signal representing energy ofsaid incoming pulse, a slicing circuit for producing a time indicationsignal when said integrated signal reaches a preset threshold level, andan output circuit responsive to said time indication signal forproducing said digital value transferred to said media accesscontroller.
 15. The network of claim 14, wherein said output circuit isresponsive to said time indication signal to reset said integrator. 16.The network of claim 14, wherein said output circuit is adapted to setsaid threshold level in response to receive signals from said inputcircuit.
 17. The network of claim 14, wherein said output circuit iscoupled to said input circuit for detecting a noise level.
 18. Thenetwork of claim 17, wherein said integrator is adapted to startintegration of said receive signal when said receive signal exceeds saidnoise level.
 19. The network of claim 14, wherein said input circuitcomprises an absolute value detector for producing an enveloperepresenting absolute value of incoming pulse amplitude.
 20. In atelephone wire network for providing data communications over telephoneline wiring in a building, a method of detecting position in time of anincoming pulse supplied from the telephone line wiring, comprising thesteps of:producing an envelope representing the absolute value ofincoming pulse amplitude, integrating the envelope over time to producean integrated signal proportional to energy of the incoming pulse, anddetecting a position in time when the integrated signal reaches a presetthreshold level to indicate a position in time corresponding to arrivalof the incoming pulse.